Originally the game didn't boot. I'm new to WINE, Proton, and Linux alike so that was expected. After looking online some more I, I found a launch option "PROTON_USE_WINED3D11=1 %command%" that turns DX11 on in WINE and the game booted fine afterward.

Now it should be noted, I'm running on a VERY low powered laptop. To be specific, it's got a GT 820m, so lag was expected. However, I got a pretty bad performance hit. I didn't expect it because this laptop runs Killing Floor just fine, but this game ran at a stable 25ish FPS on solo. I had to turn all the settings down along with the resolution to ensure the best framerate, 60+.

Overall, the game runs. And if you have better hardware, I can imagine it'll run much better for you.